I'm gearing up for a SWTOR-era (ala the MMO) Star Wars game - which I may not be recruiting for another few months - and wanted to run a stat block past people for the APC-type walker used by the Republic.

House Rule:
Each additional level of Hardened Armor lowers the attack's armor divisor by an additional step and adds another +100% to the armor's cost; Hardened 1 is double cost, Hardened 2 is triple cost, Hardened 3 is quadruple cost.

A few design notes:

First, the AT-APC has a lower center of gravity than the AT-AT seen in The Empire Strikes Back and Return of the Jedi; the leg layout is closer to that of wide-body short-leg quadruped than its later relatives. This makes it harder to be topped on its side or onto its "neck" by aircraft with tow cables.

Second, the Mid-Section Batteries. These are intended for anti-personnel fire, with one battery on the left side of the walker, the other on the right. While technically on turrets, they can't fire directly ahead or directly behind, nor are they manned.

Third, the seating. I took a look inside the parked ATs in the MMO, and counted 16 seats; I actually estimate that there's room for an additional 6-10 people standing up between them, which can be used for the rest of the platoon's gear. I didn't quite know how to stat that kind of space, so I used one additional Passenger Seating module for it.

Access to and from the cockpit is through the passenger seating. I wasn't sure if there was a third seat in the cockpit like in the ones from ESB (to my knowledge, we're never shown the cockpit of the AT-APC in the game), so I had to make a judgement call.

Here's a scaled down variant, which appears closer in size to the source material. However, the source material clearly has 16 seats in the passenger compartment, and the "head" of the walker is large enough to seat 2. If anyone can assist in making it match the source materials (2 guns on the head, two smaller guns on each side for anti-personnel, 16 seats in the passenger compartment), I'd welcome the help.

I've also reduced the armor so as to protect against small-arms, but unable to withstand anything heavier; this matches one description of the things able to be taken out by man-portable missiles to the control room.

Here's a scaled down variant, which appears closer in size to the source material. However, the source material clearly has 16 seats in the passenger compartment, and the "head" of the walker is large enough to seat 2. If anyone can assist in making it match the source materials (2 guns on the head, two smaller guns on each side for anti-personnel, 16 seats in the passenger compartment), I'd welcome the help.

If you're trying to match a stated linear dimension rather than a tonnage, keep in mind that the lengths in Spaceships are more of "guidelines" rather than actual rules. Also, heavily-armored craft may be denser (and thus smaller) than normal vessel; this is discussed in the Pyramid 3/34 article Alternate Spaceships (which you may be using already).

Another way to squeeze in more passenger space is to treat it as lacking life support. This isn't strictly RAW, but is mentioned in SS7 as an option for magical ships that don't need to be physically sealed against vacuum. It effectively doubles the capacity of cabins and seating.